Support for checking for updates

Makefile

@@ -61,3 +61,6 @@ run-demo:
 	docker build -t ipscrub .
 	docker build -t ipscrub-demo-client demo/
 	docker-compose up --abort-on-container-exit
+
+check-up-to-date: script/check-up-to-date.sh
+	$<

README.md

@@ -41,7 +41,7 @@ Scenario (2) is defended against because the server operator does not know the s
 
 `ipscrub` can be built statically with nginx or as a [dynamic module](https://www.nginx.com/blog/compiling-dynamic-modules-nginx-plus/). See the `Makefile` for examples of both ways.
 
-### Configuration
+#### Configuration
 
 In your `nginx.conf`,
 
@@ -52,10 +52,16 @@ In your `nginx.conf`,
 
 **NOTE**: nginx may still leak IP addresses in the error log. If this is a concern, disable error logging or wipe the log regularly.
 
-### Running Tests
+#### Running Tests
 
 `make test`
 
+#### Checking for Updates
+
+`make check-up-to-date`
+
+This will have a non-zero exit code if you aren't up-to-date, so you can automate regular checks.
+
 ### Changelog
 
 - 1.0.1 fixed vulnerability to unmasking hashed IPs (thanks to [@marcan](https://github.com/marcan))

script/check-up-to-date.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+echo "Checking..."
+latest=`curl "https://api.github.com/repos/masonicboom/ipscrub/releases/latest" 2>/dev/null | grep --extended-regexp -o "\"tag_name\":\s+\".*\"" | cut -d '"' -f 4`
+current=`git tag | sort | tail -n 1`
+
+if [ $current != $latest ]; then
+    echo "Current version is $current; latest is $latest. Check https://github.com/masonicboom/ipscrub/releases to see if you should update."
+    exit 1
+else
+    echo "You are on the latest version of ipscrub ($current)."
+fi